Optofluidic FRET dye laser controlled by DNA scaffolds

Abstract

We report the development of optofluidic ring resonator (OFRR) dye laser through the fluorescence resonance energy transfer (FRET) between the donor molecule labeled on an oligonucleotide and the acceptor molecule labeled on a complementary oligonucleotide. The OFRR is a thin-walled fused silica capillary with a diameter around 80 μm and a wall thickness of a few micrometers. The capillary cross-section forms a ring resonator supporting the high-Q whispering gallery modes (WGMs) with evanescent field penetrating into the capillary core, where gain medium flows through the OFRR capillary. In the OFRR FRET dye laser, the distance between donor and acceptor is controlled by the length of the DNA scaffold, which in turn determines the FRET efficiency. In this study, we investigate the lasing emission spectrum, threshold, and lasing power conversion efficiency. Cascade FRET lasing is also explored by using three dye molecules labeled on oligonucleotides. A lasing threshold as low as 5 μJ/mm2 is demonstrated with the acceptor concentration of 30 μM.